#include <iostream>
#include <cmath>
using namespace std;
int main()
{
    int apple_amount, eat_speed, time_pass;
    cin >> apple_amount >> eat_speed >> time_pass;
    if (0 == eat_speed)
    {
        if (time_pass == 0)
        {
            cout << apple_amount << endl;
        }
        else
        {
            cout << 0 << endl;
        }
    }
    else
    {
        int n = apple_amount - ((time_pass + eat_speed - 1) / eat_speed);
        cout << (n >= 0 ? n : 0) << endl;
    }
    return 0;
}